Nanostructure, compositional and magnetic studies of Poly(aniline)–CoFe2O4 nanocomposites

Abstract

Magnetic and conducting composites of cobalt ferrite nanoparticles and poly(aniline) have been synthesized in acid media by the oxidative polymerization of aniline in the presence of a dispersion of magnetic nanoparticles, using Fe(III) ions as an oxidizing agent. The materials have been characterized by X-ray diffraction studies, X-ray fluorescence, energy dispersive X-ray spectroscopy, thermogravimetric analysis, transmission electron microscopy, spectrum-imaging electron energy loss spectroscopy, conductivity and DC magnetization measurements. The composite composition and morphology depend on the aniline/magnetic nanoparticle molar ratio used during the synthesis; for composites with a low polymer content, poly(aniline) (PANI), growth occurs preferably in the vicinity of the magnetic nanoparticles, while for composites with a higher polymer content, the magnetic nanoparticles are embedded in the PANI matrix. It was also observed that iron is incorporated in the composites during their preparation. The electrical conductivities of all the synthesized materials have values in the range 1–100 S cm−1, i.e., in the metallic regime. Also, the composites feature good magnetic properties, with ferrimagnetic behavior for CoFe2O4 and the composites. The coercivity decreases as the PANI/ferrite ratio increases, indicating that poly(aniline) affects the magnetic anisotropy. All these results suggest that the morphology and the composition affect the magnetic behavior.